Single chain antibodies were engineered as potentially useful immunoteurapevhc reagents. Characterization of these single chain antibodies include (i) binding to natural ligand, (2) KD determination, and (3) stability of these proteins. In order to compare the different single chain antibodies circular dichroism and fluorescence techniques will be used the data generated from these two techniques will allow us to better understand the structural and stability differences between proteins that are homologous at the amino acid level.